AMA is voluntary. The State issues the lic. The BAR is a nationwide licensing and enforcement agency, not an association. They have no control over what is charged for fees or compensation. After that every other example you cite is a UNION. Unions were not the subject of my last post. Business associations, PACS, and political parties were. None of which can you be forced to join in order to work. That only comes with a Union and a closed shop. Afraid you were off the mark, again.
Try practicing medicine without certification, which you can only get after a 8yrs college and 2 years internship at a hospital, hospitals are almost all union, a union at its roots is a political organization and association of like minded folks. The AMA is just a great big union, that controls who, when, and what gets done medically, right or wrong.
The Bar system is not actually covered by states, but independent lawyers elected by the Bar system, not the people of each state but by member lawyers, kinda like a union isn't it. They do in fact control membership fees.
Business associations are pretty much just for politics, usually locally focused politics, for local usually retail businesses to address city/county councils, and no you are not required to join these, as they are voluntary, which is why I didn't mention them before. There are larger asso. such as the American Loggers Council, or like I hinted at before there is one for shipping/trucking but names... I'm sure the Airlines have one too.
As for Doctors Lawyers, Plumbers, Elechickens, and I'm sure a few more, they all have required tests of some sort to be licensed, that test almost always requires X years of internship, an internship that can only be attained from a UNION, then the test which UNIONS pushed for is GRADED BY THE UNION, and then sent on to the state for final certification, which is just slip of paper with fancy signatures.
Not actually sure what you are getting at as far as PACS being non political, cause I understand it to mean Political Action Committees
So yeah to be any one of the things I've mentioned, you need to be in a union, associations being unions with a bigger word, not necessarily a "closed shop" in the industrial sense, but you sure as **** are not going to just bang a sign on your door saying come on in for a discount rectal exam.